The authors examine the impact of predictors for ingroup favouritism and a positive attitude towards a university merger by conducting a longitudinal field study investigating students' perceptions of a merger. Thus, the focus of this paper lies on the developmental and dynamic aspect of social identity processes and the test of directional hypotheses in an applied setting. Based on a cross-lagged regression approach, it was shown that pre-merger identification increased favouritism, but favouritism also increased pre-merger identification. Moreover, ingroup favouritism was uni-directionally related to a negative attitude towards the merger. Contact with the merger partner revealed lagged effects on ingroup favouritism. These results confirm that issues of identity change and compatibility are crucial aspects in understanding merger adjustment and support. Copyright © 2009 John Wiley & Sons, Ltd.